The present invention relates to a sorting system having a vertical sorter in particular for conveying and sorting parcel goods such as is employed for example for conveying and sorting parcels or for sorting baggage in airports.
These vertical sorters are line sorters with a vertical reversal at the ends of the conveying line. Such vertical reversing takes place about an approximately horizontal axis. Vertical sorters are as a rule equipped with a plurality of carriages provided in succession to which one tilt tray or cross conveyor each is associated to sort out and redirect or transfer the conveyed parcel goods at predetermined or selectable points along the transport route.
Vertical sorters offer the advantage over sorting systems traveling through horizontal curves of providing a closed or very nearly closed conveying plane which facilitates conveying large-size parcel goods which extend over more than one sorting unit.
In the case of horizontal sorters including horizontal curves, parts, straps or loops sticking out from the parcel goods may get caught and jam between conveying units which may result in damage to the parcel goods or even in failure of the sorting system.
Vertical sorters offer the advantage of one continuous conveying surface in which jamming of protruding parcel goods parts is largely avoided.
Different sorting systems having vertical sorters have become known in the prior art. The sorting units of the sorting systems tend to be linked together at their front and rear ends so as to achieve on the whole a closed conveying train forming a conveying chain wherein each sorting unit comprises wheels supported on supporting rails of the sorting system. Thus each supporting unit with its associated wheels forms one chain link of the conveying chain.
The drawback of these sorting systems is the so-called polygonal effect resulting at the vertical end reversing points as the conveying chain is reversed. The reversing pulley has a circular diameter while the train of the sorting units can only pass through a polygon. The influence of the polygonal effect decreases with each sorting unit being shorter in length. This in turn increases the complexity since the quantity of the sorting units must be increased.
Furthermore, DE 697 19 044 T2 has disclosed a belt-carried tilt tray sorter with the tilting trays being spaced apart from one another in the longitudinal direction. The tilt trays are supported on an elastic conveyor belt supported by a slider bed for taking up and diverting the supporting forces.
For sorting out the parcel goods this known system uses movable trip members which can be positioned in the traveling path of an actuator to cause one side of the tray to lift, discharging the parcel goods.
The drawback of this known system is the mechanically controlled parcel goods discharge since the tilt tray control speed depends on the moving speed of the vertical sorter. Furthermore considerable acoustic pollution is involved due to the movable trip member hitting on the actuator of the tilt tray.
Another drawback of the known prior art is the flexibility of the endless conveyor belt which only allows limited prestressing since its elasticity causes elongation in the conveyor belt which will further increase with continuing operation.